NullPointerException when using getSupportActionBar

Question

I am trying to implement a simple navigation drawer in my Android app but I am not able to solve a certain bug.

Attempting to run an app throws a NullPointerException:

Process: com.emertonalex.whiskynotes04, PID: 22225
              java.lang.RuntimeException: Unable to start activity ComponentInfo{com.emertonalex.whiskynotes04/com.emertonalex.whiskynotes04.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
                  at android.app.ActivityThread.-wrap11(Unknown Source:0)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
                  at android.os.Handler.dispatchMessage(Handler.java:106)
                  at android.os.Looper.loop(Looper.java:164)
                  at android.app.ActivityThread.main(ActivityThread.java:6494)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
                  at com.emertonalex.whiskynotes04.MainActivity.setupToolbar(MainActivity.java:320)
                  at com.emertonalex.whiskynotes04.MainActivity.onCreate(MainActivity.java:97)
                  at android.app.Activity.performCreate(Activity.java:6999)
                  at android.app.Activity.performCreate(Activity.java:6990)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
                  at android.app.ActivityThread.-wrap11(Unknown Source:0) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
                  at android.os.Handler.dispatchMessage(Handler.java:106) 
                  at android.os.Looper.loop(Looper.java:164) 
                  at android.app.ActivityThread.main(ActivityThread.java:6494) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

As far as I see it the getSupportActionBar() function call that messes stuff up. I tried covering the call with the "assert" in setupToolbar() and it seems like it passes that stage and fails at the

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

The pieces of code themselves that call the getSupportActionBar() are these:

In MainActivity

protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.add_notes);
   ...
   setupToolbar();

   getSupportActionBar().setDisplayHomeAsUpEnabled(false);
   getSupportActionBar().setHomeButtonEnabled(true);
   ...
}

And

void setupToolbar(){
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    assert getSupportActionBar() != null;
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

I am new to Android/Java dev and would be very appreciative of any help. Also, it would be great if you tell me why this error appears, to begin with, so I can avoid it in the future.

Thank you

score 0 · Accepted Answer · answered Dec 31 '17 at 21:59

0

Changing from Support Action Bar to ActionBar should fix the issue:

getActionBar().setDisplayHomeAsUpEnabled(true);

answered Dec 31 '17 at 21:59

beastlyCoder

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Thanks for answering! Unfortunately, the error still persists. Exactly the same type of error pointing at the now new getActionBar().setDisplayHomeAsUpEnabled(true); in setupToolbar() – Alex Emerton Jan 01 '18 at 22:31

NullPointerException when using getSupportActionBar

1 Answers1